<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <select id="sel">
        <option value="1">Apple</option>
        <option value="2">Pear</option>
        <option value="3">Banana</option>
        <option selected value="4">Orange</option>
    </select>

    <script src="../js/jquery1.11.3.js"></script>
    <script>
        
        
        let selectValue=$('#sel :selected').val()//下拉框selected 里面value值
        let selectValue1=$('#sel').val() //直接选中下拉框selected value值

        let selectText=$('#sel :selected').text() //下拉框selected文本
        let selectText1=$('#sel').text() // 下拉框里面所有option选项里面的值
        
        // onchange事件
        $('#sel').change(function(){
            let selValue=$(this).val() //找到再次选中的value值
            // 找到被选中的option元素？
            // 找到再次选中opton的text值
           
          
          
        })


    </script>

</body>

</html>